1. Field of the Invention
The present invention relates generally to telecommunication systems and more particularly to a method and system for preserving service node resources and reducing clipping effect associated with the provision of an advanced intelligent network service such as a simultaneous ringing service.
2. Background of the Invention
Under the current advanced intelligent network (AIN) structure, a typical telephone call originated by a calling party results in the ringing of the called party's telephone unless the called party subscribes to certain AIN services, such as call forwarding, privacy screening, and messaging, each of which manages an incoming call in a unique manner. AIN structures are described in U.S. Pat. No. 5,701,301, which is hereby incorporated by reference.
A call forwarding service allows a subscriber to answer a call at a telephone different from the telephone for which the call was intended. For example, a telephone customer with a subscription to a call forwarding service can receive a call intended for his home telephone at any location he desires as long as he remembers to activate the call forwarding service by supplying a forwarding telephone number. Typically, a subscriber would designate a telephone at which he would receive all calls intended for his home telephone. Although the call forwarding service allows the subscriber the opportunity to answer the call, such opportunity does not always materialize. For example, if the person answering a forwarded telephone call is not the subscriber, that person might say “wrong number,” and the subscriber would be deprived of the opportunity to accept the call.
If the subscriber has a wireless telephone, he could potentially solve the above-identified problem by designating his wireless telephone to receive all forwarded calls from his home wireline telephone. This “solution,” however, creates new problems. For example, if the subscriber, having activated the call forwarding service, returns home without deactivating the call forwarding service and having his wireless telephone turned off, he will not be able to receive any calls. Furthermore, even if the subscriber stays home with his wireless telephone turned on, he would be answering a telephone call intended for his wireline telephone using his wireless telephone. In this situation, the subscriber would be paying a higher wireless telephone bill due to the higher rates associated with wireless services. Similarly, the subscriber might be using his wireless telephone unnecessarily when someone at his home could have answered the telephone intended for the home telephone.
Attempts have been made to solve the above problems by providing simultaneous ringing services to multiple telephones of a customer. For example, U.S. Pat. No. 5,206,901 (Harlow) discloses a system for alerting multiple telephones in response to an incoming call to a subscriber's primary telephone. U.S. Pat. No. 5,502,762 (Andrew) discloses a telephone device that, in addition to routing the call to a first telephone, generates additional calls to one or more additional telephones. U.S. Pat. No. 5,802,160 (Kugell) discloses a method in which a telephone service subscriber has greater flexibility in the management of the multiple telephones receiving simultaneous ringing services.
With the exception of Harlow (which does not use a service node), all the above identified prior art patents use up valuable telecommunication resources each time multiple calls are initiated regardless of whether the telephones are busy or idle. For example, three ports are tied up when two simultaneous calls are initiated to telephones that are busy, i.e., unavailable to receive calls. In these prior art inventions, the multiple outgoing calls use up resources even when the subscriber receives no real benefit from the service. For example, when one or more of the call-receiving telephones are busy, in which case a call to the busy telephone or telephones would have been unnecessary, the inventions disclosed in the references would nonetheless initiate calls to these “busy” telephones and thereby use up resources in the telecommunication system. In some cases, the subscriber might also be billed for those unnecessary calls. Furthermore, none of the prior art references identified above helps a subscriber who does not wish to receive calls on any of his secondary telephones when his primary telephones is busy. In summary, none of the references provides a resource-conserving method in which multiple calls are generated only when the primary and the secondary telephones are idle.
Attempts have also been made to use a service node in the advanced intelligent system to place multiple calls simultaneously. One problem associated with using a service node to make simultaneous calls is the so-called “clipping effect” that cuts off the first few seconds of a communication. The clipping effect occurs when the service node withdraws from the circuit after establishing a communication between a calling party and a called party through their service switching points. In addition to being somewhat annoying, the clipping effect could also result in the following negative effects:                (1) The called party does not get an immediate response from the calling party after the called party answers the call. This may cause the called party abandon the call thinking that someone must have dialed a wrong number.        (2) The calling party does not hear anything on her handset for about three seconds after the audible tone stops. This may cause the calling party to abandon the call thinking that the call has been disconnected by the called party.        (3) The called party's answering machine answers the call, and the calling party misses the greeting message. This may cause the calling party to hang up the telephone instead of leaving a message.        
There is currently no effective solution for eliminating or reducing the clipping effect caused by call transferring by a service node.
Accordingly, there is a need for a method to conserve service node resources in the provision of AIN services such as simultaneous ringing service. In addition, there is also a need for reducing the clipping effect associated with the provision of AIN services using a service node.